Electronics > Beginners
Just how bad is it? Audio mixer with headphone amp.
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BrianHG:
Maybe you should use TI's balanced input high fidelity amplifier design in the PCM5242's example schematic in it's data sheet.  It goes to the volumes that you want and is faster than the OPA551 and it is stereo.  However, to get that full quality, you will need to go all balanced audio for that part of your circuit.  3X cheaper, and more power (1 watt for +/-15v supply), higher frequency than the OPA551.  However, to compare the 2, you would need to convert % distortion for the OPA551 to distortion measured in db for the tpa6120a2.  In fact, the tpa6120a2 roasts your NE5532s to such an absurd degree, so, maybe you don't need such a high quality headphone amp on a mixing console where the sound previously goes through multiple NE5532s.  (In audio applications & driving headphones/line level)
paulca:
Confession of a blonde moment.

I was concerned about the high current draw.  That current being measured by the INPUT from the bench supply to the dual rail PSU.

Well, of course I forgot to factor the voltage difference.

Highest current pull of the PSU was 70mA.  25mA is the stated idle quiescent input current, but I was reading more like 30mA.  Even if we take the 25mA and subtract that from the 70mA seen...

70-25mA = 45mA
45mA * 12V = 0.540W
0.540W / 30V = 18mA

The opamps are rated for +-10mA, there are two ICs on the circuit + a small amount dropped in the various passives, so they are not being exceeded.  They may be higher than expected, which might be the HF noise I'm dealing with in another thread, I hope, but it's all good.
BrianHG:
This one was made just for you: https://www.ebay.com/itm/Douk-Audio-PCM1794A-DAC-Decoder-Balanced-HiFi-Parallel-Board-192K-Gold-plated/272982323436?epid=28011370612&hash=item3f8f03b0ec:g:ZKIAAOSwBkRaMjTA

Take a look at the op-amps.
This board has a SNR of 132db since it uses each dac in balanced mode out & is converted to unbalanced using your NE5532s.
Though, you are limited to 24 bit, 192Khz sample rate.  But, this is plenty enough.

In mono mode, that DAC outputs 9v RMS.
paulca:
I thought I was the overkill suspect?

You seem as overkill on the DACs as I am on active volume controls.  :-DD

I think a TI PCM290x will do me just fine.  All I need to do is minimize noise pick up from the PC ground.
BrianHG:

--- Quote from: paulca on March 05, 2018, 11:35:17 pm ---You seem as overkill on the DACs as I am on active volume controls.  :-DD

--- End quote ---
;D That's because if you checked the data sheet on the 32bit 4$ DACs, you would see they have a built in pre-amp volume control which can be set through I2C.  No sketchy wired pots in my design.
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